Debugging Ajax / Dynamic HTML

So I have some javascript that I've been working on that makes changes to a page dynamically. Using the 'View Source' option of a browser on a dynamically loaded page will show you the source BEFORE any changes were made.

Is there any tool that any of you know of that will show you the source in REAL-TIME? Firebug doesn't do it, or it atleast it appears not to.. now that I think of it it'd be a super useful tool (and would be worth making if it doesn't exist).